U.S. published patent application No. 20030230266A1 entitled VCT SOLENOID DITHER FREQUENCY CONTROL by Ekdahl, Earl et al discloses a method that uses a dither signal for reducing hysteresis effect in a variable cam timing system is provided. The method includes the steps of: a) providing a dither signal having at least two switchable frequencies; b) determining the frequency characteristics of an engine speed; c) determining at least one frequency beating point in relation to a neighborhood of an engine crank RPM values; and d) changing the dither signal frequency when the engine is operating within the neighborhood of the engine crank RPM values. Thereby frequency beating effect is reduced.
U.S. published patent application No. 20040003788A1 entitled CONTROL METHOD FOR ELECTRO-HYDRAULIC CONTROL VALVES OVER TEMPERATURE RANGE by Taylor, Danny et al discloses a variable cam timing (VCT) system which has a feedback control loop wherein an error signal relating to at least one sensed position signal of either a crank shaft position or at least one cam shaft position is fed back for correcting a predetermined command signal. The system further includes a valve for controlling a relative angular relationship of a phaser; and includes a variable force solenoid for controlling a translational movement of the valve. An improved control method comprising the steps of: providing a dither signal sufficiently smaller than the error signal; as temperature varies, changing at least one parameter relating to the dither signal; and applying the dither signal upon the variable force solenoid, thereby using the dither signal for overcoming a system hysteresis without causing excessive movement of valve.
European Patent No. 1375838A2 entitled CONTROL METHOD FOR TRANSITIONS BETWEEN OPEN AND CLOSED LOOP OPERATION IN ELECTRONIC VCT CONTROL by Quinn, Jr., Stanley B et al discloses a Variable Cam Timing (VCT) control system, there are conditions when the system must operate in an open-loop mode, and other situations where closed-loop operation is desired. A number of operating states is provided for VCT control system to switch between the states. A control methodology for switching between these two modes of operation, with minimal disturbances, is described. Further, during switching from open loop to closed loop, a scheme that impedes the impact upon the VCT system is provided.
U.S. published patent application No. 20040040525A1 entitled Method to reduce noise of a cam phaser by controlling the position of center mounted spool valve by Simpson, Roger discloses a method to reduce the noise caused by torsional reversals of a rotor hitting the phaser housing in a VCT cam timing system. A cam torque actuated phaser (phaser with check valves) the control loop is opened and rather then moving the spool valve to one end or the other end, the spool valve is moved just slightly off null. By doing this the oil ports in the spool passageways that control the motion of the phaser are restricted and the motion of the phaser is reduced. Therefore the noise of the phaser is reduced.
U.S. published patent application No. 20030230263A1 entitled VCT cam timing system utilizing calculation of intake phase for dual dependent cams by Ekdahl, Earl et al discloses an engine with dependent intake cams requires a different method and formula to determine the phase of the intake cams. The exhaust camshaft drives the intake camshaft and so the intake cam position is dependent upon the exhaust cam position. The present invention provides a VCT cam timing system utilizing calculation of intake phase for dual dependent cams.
U.S. Pat. No. 6,666,181 entitled Hydraulic detent for a variable camshaft timing device by Smith, Franklin R.; et al discloses a phaser which includes a housing and a rotor disposed to rotate relative to each other is provided. The housing has at least one cavity disposed to be divided by a vane rigidly attached to the rotor. The vane divides the cavity into a first chamber and a second chamber. The phaser further includes passages connecting the first and the second chamber, thereby facilitating the oscillation of the vane within the cavity. The phaser includes: a) a valve disposed to form at least two openings for fluid flowing between the first chamber and the second chamber and being disposed to keep at least one opening closed; and b) at least one by-pass disposed to stop or slow down the rotation between the housing and the rotor, thereby allowing a locking mechanism to lock the housing and the rotor together independent of fluid flow.
U.S. published patent application No. 20030230262A1 entitled Control method for achieving expected VCT actuation rate using set point rate limiter by Quinn, Jr., Stanley B teaches in a VCT system having a feedback loop for controlling a phaser angular relationship, a control law disposed to receive a plurality of set point values and a plurality of feed back values is provided to include: a computation block for receiving the plurality of set point values as inputs, the computation block outputting a first output and a second output; a first summer for summing the first output and the plurality of feed back values to produce a first sum (e0); a phase integrator and a phase compensator receiving the first sum (e0) and derivatives (e1) thereof outputting a processed value (e2); a amplifier amplifying the second output by a predetermined scale (Kff); and e) a second summer for summing the processed value (e2) and the amplified second output to produce a second sum (e3).
U.S. Pat. No. 6,668,778 entitled Using differential pressure control system for VCT lock by Smith, Franklin R. discloses a variable cam timing system comprising a VCT locking pin in hydraulic communication with the control circuit of the differential pressure control system (DPCS) is provided. When the control pressure is less than 50% duty cycle the same control signal commands the locking pin to engage and the VCT to move toward the mechanical stop. When the control pressure is greater than 50% duty cycle the locking pin disengages and the VCT moves away from the mechanical stop.
U.S. Pat. No. 6,263,846 entitled Control valve strategy for vane-type variable camshaft timing system by Simpson, Roger et al discloses an internal combustion engine includes a camshaft and hub secured to the camshaft for rotation therewith, where a housing circumscribes the hub and is rotatable with the hub and the camshaft, and is further oscillatable with respect to the hub and camshaft. Driving vanes are radially inwardly disposed in the housing and cooperate with the hub, while driven vanes are radially outwardly disposed in the hub to cooperate with the housing and also circumferentially alternate with the driving vanes (to define circumferentially alternating advance and retard chambers. A configuration for controlling the oscillation of the housing relative to the hub includes an electronic engine control unit, and an advancing control valve that is responsive to the electronic engine control unit and that regulates engine oil pressure to and from the advance chambers. A retarding control valve responsive to the electronic engine control unit regulates engine oil pressure to and from the retard chambers. An advancing passage communicates engine oil pressure between the advancing control valve and the advance chambers, while a retarding passage communicates engine oil pressure between the retarding control valve and the retard chambers.
U.S. published patent application No. 20030196625A1 entitled Air venting mechanism for variable camshaft timing devices by Smith, Franklin R.; discloses a device includes: a locking member substantially disposed within a closure in the housing, the locking member locking the housing and the rotor free from relative rotation and independent of fluid flow; and at least one vent passage disposed between either the first or the second chamber and the closure in the housing; thereby air within the chamber is purged and noise stopped.
Furthermore, U.S. published patent application No. 20030192518A1 entitled SYSTEM AND METHOD FOR EXHAUST GAS RECIRCULATION CONTROL by Gopp, Alexander Yuri et al discloses a system and method for controlling a multi-cylinder internal combustion engine having at least one automatically controllable airflow actuator and an exhaust gas recirculation (EGR) system including an EGR valve include determining a desired manifold pressure based at least in part on position of the automatically controllable airflow actuator and controlling the EGR valve such that a measured manifold pressure approaches the desired manifold pressure. In one embodiment, the automatically controllable airflow actuators include a charge motion control valve and a variable cam timing device. In other embodiments, the automatically controllable airflow actuators may include variable valve lift devices, variable valve timing devices, or any other device that affects the residual exhaust gases within the cylinders.
However, no prior art patents or publications using on/off solenoid use a predefined entity having a level being preset is disclosed or taught. Therefore, it is desirous to have an on/off solenoid in a feedback control loop, wherein a switching variable is provided, and a calculation based on the sign of the switch's numerical value is also provided for turning on or off the two-position ON/OFF solenoid.